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| United States Patent |
6,259,495
|
|
Maeda
|
July 10, 2001
|
Liquid crystal display panel and method of manufacturing the same,
including a structure for, and a method of preparing, terminal or
connecting electrodes for connecting liquid crystal display panel to an
external drive circuit
Abstract
A simple method for preventing oxidization of an aluminum surface of
terminal electrode, increase of pressure contact resistance, unstability
and reduction of connection reliability is provided. In a terminal
electrode part on a reactive matrix substrate, for being connected to an
external drive circuit, connecting electrodes are formed by using aluminum
or an aluminum alloy, at least their surfaces connected to TCP are covered
with an insulating film of aluminum oxide or consisting of a laminate film
of aluminum oxide aluminum hydroxide, and the insulating film is
selectively removed in a step subsequent to the final step in a cell
formation process. In this way, adverse effects of the heat treatment
processes such as the annealing in the array formation process and the
orientation film sintering of the cell formation process and the
oxidization of the connecting electrode surface in the washing.
| Inventors:
|
Maeda; Akitoshi (Tokyo, JP)
|
| Assignee:
|
NEC Corporation (Tokyo, JP)
|
| Appl. No.:
|
233961 |
| Filed:
|
January 20, 1999 |
Foreign Application Priority Data
| Jan 20, 1998[JP] | 10-008718 |
| Current U.S. Class: |
349/42; 257/59; 349/149; 349/152 |
| Intern'l Class: |
G02F 001/136 |
| Field of Search: |
349/42,149,152,43,141
257/59,72,761,763
|
References Cited
U.S. Patent Documents
| 5148248 | Sep., 1992 | Possin et al. | 357/23.
|
| 5264728 | Nov., 1993 | Ikeda et al. | 257/761.
|
| 5296653 | Mar., 1994 | Kiyota et al. | 174/250.
|
| 5316975 | May., 1994 | Maeda | 437/195.
|
| 5428250 | Jun., 1995 | Ikeda et al. | 257/761.
|
| 5614728 | Mar., 1997 | Akiyama | 257/57.
|
| 5821622 | Oct., 1998 | Tsuji et al. | 257/763.
|
| 5886761 | Mar., 1999 | Sasaki et al. | 349/122.
|
| 5917198 | Jun., 1999 | Maeda | 257/59.
|
| 5943559 | Aug., 1999 | Maeda | 438/149.
|
| 6043859 | Mar., 2000 | Maeda | 349/143.
|
| Foreign Patent Documents |
| 60-260920 | Dec., 1985 | JP.
| |
| 3-240027 | Oct., 1991 | JP.
| |
| 03280021A | Dec., 1991 | JP.
| |
| 6-148658 | May., 1994 | JP.
| |
| 6-273782 | Sep., 1994 | JP.
| |
| 7-325321 | Dec., 1995 | JP.
| |
| 8-179372 | Jul., 1996 | JP.
| |
| 9-244055 | Sep., 1997 | JP.
| |
| 9-293877 | Nov., 1997 | JP.
| |
Primary Examiner: Sikes; William L.
Assistant Examiner: Chowdhury; Tarifur R.
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas, PLLC
Claims
What is claimed is:
1. A liquid crystal display panel including an active matrix substrate,
another substrate facing the active matrix substrate and a liquid crystal
intervening between the two substrates, wherein:
the active matrix substrate comprises a transparent substrate, on which a
plurality of scan lines, a plurality of signal lines crossing the scan
lines, switching elements provided at the intersections of the scan lines
and signal lines, pixel electrodes connected to the switching elements and
connecting electrodes provided on leading end portions of the scan lines
and signal lines are formed; and
at least a connecting part of the connecting electrodes is formed by using
aluminum or alloy mainly composed thereof,
wherein a protective insulating film is formed on at least the connecting
electrodes and has terminal contact holes reaching the connecting part of
the connecting electrodes, and
wherein the connecting part is a connection with respect to an external
drive circuit.
2. A liquid crystal display panel including an active matrix substrate,
another substrate facing the active matrix substrate and a liquid crystal
intervening between the two substrates, wherein:
the active matrix substrate comprises a transparent substrate, on which a
plurality of scan lines, a plurality of signal lines crossing the scan
lines, switching elements provided at the intersections of the scan lines
and signal lines, pixel electrodes connected to the switching elements,
opposite electrodes and connecting electrodes provided on leading end
portions of the scan lines and signal lines are formed; and
at least a connecting part of the connecting electrodes is formed by using
aluminum or alloy mainly composed thereof,
wherein a protective insulating film is formed on at least the connecting
electrodes and has terminal contact holes reaching the connecting part of
the connecting electrodes, and
wherein the connecting part is a connection with respect to an external
drive circuit.
3. A liquid crystal display panel including an active matrix substrate,
another substrate facing the active matrix substrate and a liquid crystal
intervening between the two substrates, wherein:
the active matrix substrate comprises a transparent substrate, on which a
plurality of signal lines, switching elements provided on the signal
lines, pixel electrodes connected to the switching elements and connecting
electrodes provided on leading end portions of the signal lines are
formed; and
at least a connecting part of the connecting electrodes is formed by using
aluminum or alloy mainly composed thereof,
wherein a protective insulating film is formed on at least the connecting
electrodes and has terminal contact holes reaching the connecting part of
the connecting electrodes, and
wherein the connecting part is a connection with respect to an external
drive circuit.
4. A liquid crystal display panel including an active matrix substrate,
another substrate facing the active matrix substrate and a liquid crystal
intervening between the two substrates, wherein:
the active matrix substrate comprises a transparent substrate, on which a
plurality of scan lines, a plurality of signal lines crossing the scan
lines, switching elements provided at the intersections of the scan lines
and signal lines, pixel electrodes connected to the switching elements and
connecting electrodes provided on leading end portions of the scan lines
and signal lines are formed;
at least a connecting part of the connecting electrodes is formed by using
aluminum or alloy mainly composed thereof; and
in an active matrix substrate area with the intervening liquid crystal
present therein, an insulating film covers the surfaces of uppermost layer
scan lines, signal lines and electrodes of the switching elements,
wherein the insulating film consists of laminate film of aluminum oxide and
aluminum hydroxide, and
wherein the connecting part is a connection with respect to an external
drive circuit.
5. A liquid crystal display panel including an active matrix substrate,
another substrate facing the active matrix substrate and a liquid crystal
intervening between the two substrates, wherein:
the active matrix substrate comprises a transparent substrate, on which a
plurality of scan lines, a plurality of signal lines crossing the scan
lines, switching elements provided at the intersections of the scan lines
and signal lines, pixel electrodes connected to the switching elements,
opposite electrodes and connecting electrodes provided on leading end
portions of the scan lines and signal lines are formed;
at least a connecting part of the connecting electrodes is formed by using
aluminum or alloy mainly composed thereof; and
in an active matrix substrate area with the intervening liquid crystal
present therein, an insulating film covers the surfaces of uppermost layer
scan lines, signal lines, electrodes of the switching elements and opposed
electrodes,
wherein the insulating film consists of laminate film of aluminum oxide and
aluminum hydroxide, and
wherein the connecting part is a connection with respect to an external
drive circuit.
6. A liquid crystal display panel including an active matrix substrate,
another substrate facing the active matrix substrate and a liquid crystal
intervening between the two substrates, wherein:
the active matrix substrate comprises a transparent substrate, on which a
plurality of signal lines, a plurality of switching elements provided at
the plurality of signal lines, pixel electrodes connected to the switching
elements and connecting electrodes provided on leading end portions of the
signal lines are formed;
at least a connecting part of the connecting electrodes is formed by using
aluminum or alloy mainly composed thereof; and
portions of the signal lines in an area with the intervening liquid crystal
therein are covered by an insulating film,
wherein the insulating film consists of laminate film of aluminum oxide and
aluminum hydroxide, and
wherein the connecting part is a connection with respect to an external
drive circuit.
7. The liquid crystal display panel according to one of claims 4 to 6,
wherein a protective insulating film is formed on at least the connecting
electrodes and has terminal contact holes reaching the connecting
electrodes.
8. The liquid crystal display panel according to one of claims 4 to 6,
wherein no protective insulating film is formed on the connecting
electrodes.
Description
BACKGROUND OF THE INVENTION
The present invention relates to liquid crystal display panels for liquid
crystal displays and, more particularly, the structure of and method of
preparing terminal or connecting electrodes for connecting such a display
panel to an external drive circuit.
Up to date, liquid crystal displays which feature small thickness and light
weight, particularly active matrix liquid crystal displays which have
switching elements each provided for each pixel, have been extensively
used. The extensive use of active matrix liquid crystal displays is
attributable to their general features that they are capable of readily
providing gradations, quickly responsive and suited for displaying moving
images. As the switching element are used thin film transistors (TFT) and
MIM elements.
FIG. 14 is a sectional view showing an active matrix liquid crystal
display. The illustrated active matrix liquid crystal display comprises an
active matrix substrate 1 having switching elements, another substrate 2
parallel to and spaced apart by about 50 .mu.m from the substrate 1, and
liquid crystal 4 filling a space defined by the substrates 1 and 2 and a
seal 3. Polarizing sheets 5 are each bonded to the outer surface of each
of the substrates 1 and 2.
FIG. 15 is a view showing the electric configuration of an active matrix
liquid crystal display panel using TFTs. The illustrated active matrix
liquid crystal display panel using the TFTs, comprises pluralities of scan
lines 12 and signal lines 13, which are formed in crossing relation to one
another on a transparent substrate 11, and the TFTs 14 provided at the
intersections of the lines 12 and 13. The TFT 4 is a three-terminal
element, which comprises a switching semiconductor layer and a gate, a
source and a drain electrodes. Pixel electrodes 15, each connected to each
TFT 14, are provided in a matrix array. For connecting the display panel
to an external drive circuit, scan line terminals 16 are provided on the
leading ends (i.e., one side) of the scan lines 12, and signal line
terminals 17 are provided on the leading ends (i.e., one side) of the
signal lines 13. The external drive circuit is usually electrically
connected to the display panel by press bonding the two via a tape carrier
package (TCP) and an isotropic conductive film (ACF), the TCP being
provided on the circuit side, the ACF being provided on the terminal
surface side.
Referring to FIG. 15, for instance, when a scan line Xi among the scan
lines 12 is selected and activated by voltage pulse application, the TFTS
14 connected to this scan line are simultaneously turned on with a
resultant increase of their gate voltage beyond a threshold voltage, and
signal voltage corresponding to image data is transmitted from each signal
line 13 through the source of each "on" TFT 14 to the drain thereof. The
signal voltage transmitted to the drain produces a voltage difference
between the pixel electrode 15, which is connected to the drain, and the
opposed electrode 19 facing the pixel electrode 15 via the intervening
liquid crystal layer 18, thus changing the light permeability thereof for
image display.
In a liquid crystal display of lateral electric field type, the opposed
electrode 19 is provided on the TFT substrate side. In this display, when
the selected scan line Xi is restored to the non-selected state so that
the gate voltage becomes lower than the threshold voltage, the gates of
all the TFTs 14 connected to this scan line are turned off at a time, and
then the next scan line Xi+1 is selected, and the gates of the TFTs 14
connected to this scan line are turned on, thus bringing about an
operation like that described above.
After the gates have been turned off, the voltage difference between the
pixel electrode 15 and the opposed electrode 19 is accumulated in the
inter-electrode electrostatic capacitance and held in the liquid crystal
layer 18 until the same scan line is selected and activated afresh by
voltage pulse application.
In the active matrix substrate which uses amorphous silicon (a-Si) for the
semiconductor layer and utilizes TFTs or MIM elements, connecting
terminals (i.e., scan line terminals 16 and signal line terminals 17) are
provided on the leading ends of the scan lines and signal lines for
connecting the display panel to the external drive circuit. In the case of
utilizing TFTs, the above operation is brought about.
Requirements for the connecting terminals are that the connection
resistance at the terminal part is low and stable, that high reliability
can be ensured against intrusion of water or the like from the outside and
that a press bonding process can be readily carried out afresh.
By way of example, Japanese Patent Laid-Open No. 60-260920 discloses a
method, in a liquid crystal display of thermal write type, of forming an
aluminum hydroxide cover film on heating electrodes by using aluminum or
an alloy thereof.
FIG. 17 shows the method described in the Japanese Patent Laid-Open No.
60-260920. In this method, after formation on a transparent substrate 11
of stripe-like heating electrodes 171 of aluminum or an alloy thereof, the
resultant substrate is hot water treated in pure water at 50 to 100
degrees C, and then an aluminum hydroxide cover film is formed to a
thickness of 0.1 to 1 .mu.m on the surface of the heating electrodes 171.
In the hot water treatment, on the terminal electrode was formed the photo
resist pattern and the aluminum hydroxide is not formed thereon.
Japanese Patent Laid-Open No. 3-280021 discloses an electro-optical
apparatus, which uses aluminum or like corrosion-resistant metal for the
terminal electrode part. FIG. 18 shows the discloses electro-optical
apparatus. As shown in the Figure, on a transparent substrate 11 are
formed a pixel electrode (not shown), a non-linear resistance layer 181,
an upper electrode (not shown) of chromium, a column electrode 182, a
terminal electrode 184 of aluminum.
Aluminum and its alloys is usually readily subject to corrosion. However,
even by directly forming the terminal electrode in this way, relatively
satisfactory reliability can be maintained against external water
intrusion.
As a further example, Japanese Patent Laid-Open No. 8-12282 discloses a
technique concerning a thin film transistor substrate, which has scan
lines and gate electrodes formed by using aluminum or an alloy thereof and
covered by an anodic oxidization film. This technique features
satisfactory anodic oxidization film boundary controllability with respect
to the gate terminal part. FIG. 19 illustrates this technique. As shown in
the Figure, on a transparent substrate 11 are formed a scan line 12, a
signal line 13, a TFT 14 and a pixel electrode 15. The scan line 12 and
the gate of the TFT 14 are formed by using aluminum or an alloy thereof.
Scan line terminal part 16 is formed by laminating aluminum or an alloy
thereof, titanium or tantalum and indium tin oxide (ITO). The scan line 12
and gate electrode are covered by an anodic oxidization film of aluminum,
which is formed by an anodic oxidization process in the presence of a
titanium layer having been formed.
Japanese Patent Laid-Open No. 43-232274 also discloses a method, which is
used for a thin film transistor substrate using aluminum or an alloy
thereof for scan lines and gate electrodes for covering these desired
parts with an anodic oxidization film.
The prior art techniques disclosed in the Japanese Patent Laid-Opens No.
60-260920 and No. 3-280021, however, have a problem that an additional
photo-lithographic process is necessary for the following reasons.
According to the Japanese Patent Laid-Open No. 60-260920, it is necessary
to carry out the hot water process by forming a photo-resist pattern on
the terminal electrode part. According to the Japanese Patent Laid-Open
No. 3-280021 it is necessary to convert chromium low electrodes in the
terminal electrode part to aluminum.
Another problem posed in these techniques is that the electric connection
between the terminal electrode part and the TCP may not be obtained or may
result in high and unstable connection resistance (or forced contact
resistance). This is so because in either technique an insulating layer
may be formed on aluminum, as a result of possible oxidization of the
aluminum surface in annealing that is carried out in the final step of an
array process or orientation film sintering carried out in a cell
formation process (due to highly possible exposure of the substrate at a
high temperature to air for temperature reduction after the thermal
process), or possible oxidization or hydroxidization of the aluminum
surface in washing carried out in the cell formation process (due to
highly provable rinsing with hot water or steam drying the substrate after
the washing).
A further problem is possible irregular display or reduction of the yield
and reliability. This is so because it is impossible to use alkali or acid
in the washing carried out in the cell formation process (for the aluminum
of the terminal electrode part is etched by alkali or acid), thus
resulting in insufficient removal of alkali ions or acid ions so that the
residual ions migrate into and remain in the liquid crystal.
A still further problem is the generation of hillocks in the aluminum of
the terminal electrode part, resulting in damages to the orientation film
of the element part or contamination of rubbing roll in rubbing carried
out in the cell formation process. This is so because the hillocks which
have been generated during the annealing in the alloy process or the
orientation film sintering in the cell formation process, are squeezed and
to be drown up to the element part and attached to the rubbing roll during
the rubbing.
The techniques disclosed in the Japanese Patent Laid-Opens No. 8-122822 and
No. 3-232274 have a problem that an additional photo-lithographic process
is necessary, thus leading to a cost increase. This is so because
according to the Japanese Patent Laid-Open No. 8-122822 the titanium or
tantalum film in the terminal electrode part should be patterned, and
according to the Japanese Patent Laid-Open No. 3-232274 the aluminum scan
lines in the terminal electrode part should be converted to chromium or
tantalum.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a liquid crystal display
panel, which can ensure low and stable resistance of forced contact of the
terminal electrode part with the TCP and high connection reliability, and
requires no additional process, and also a method of manufacturing the
same.
According to a first aspect of the present invention, there is provided a
liquid crystal display panel including an active matrix substrate, another
substrate facing the active matrix substrate and liquid crystal
intervening between the two substrates, wherein:
the active matrix substrate comprises a transparent substrate, on which a
plurality of scan lines, a plurality of signal lines crossing the scan
lines, switching elements provided at the intersections of the scan lines
and signal lines, pixel electrodes connected to the switching elements and
connecting electrodes provided on leading end portions of the scan lines
and signal lines are formed; and
at least a connecting part of the connecting electrodes is formed by using
aluminum or alloy mainly composed thereof.
According to a second aspect of the present invention, there is provided a
liquid crystal display panel including an active matrix substrate, another
substrate facing the active matrix substrate and liquid crystal
intervening between the two substrates, wherein:
the active matrix substrate comprises a transparent substrate, on which a
plurality of scan lines, a plurality of signal lines crossing the scan
lines, switching elements provided at the intersections of the scan lines
and signal lines, pixel electrodes connected to the switching elements,
opposite electrodes and connecting electrodes provided on leading end
portions of the scan lines and signal lines are formed; and
at least a connecting part of the connecting electrodes is formed by using
aluminum or alloy mainly composed thereof.
According to a third aspect of the present invention, there is provided a
liquid crystal display panel including an active matrix substrate, another
substrate facing the active matrix substrate and liquid crystal
intervening between the two substrates, wherein:
the active matrix substrate comprises a transparent substrate, on which a
plurality of signal lines, switching elements provided on the signal
lines, pixel electrodes connected to the switching elements and connecting
electrodes provided on leading end portions of the signal lines are
formed; and
at least a connecting part of the connecting electrodes is formed by using
aluminum or alloy mainly composed thereof.
According to a fourth aspect of the present invention, there is provided a
liquid crystal display panel including an active matrix substrate, another
substrate facing the active matrix substrate and liquid crystal
intervening between the two substrates, wherein:
the active matrix substrate comprises a transparent substrate, on which a
plurality of scan lines, a plurality of signal lines crossing the scan
lines, switching elements provided at the intersections of the scan lines
and signal lines, pixel electrodes connected to the switching elements and
connecting electrodes provided on leading end portions of the scan lines
and signal lines are formed;
at least a connecting part of the connecting electrodes is formed by using
aluminum or alloy mainly composed thereof; and
in an active matrix substrate area with the intervening liquid crystal
present therein, an insulating film covers the surfaces of uppermost layer
scan lines, signal lines and electrodes of the switching elements.
According to a fifth aspect of the present invention, there is provided a
liquid crystal display panel including an active matrix substrate, another
substrate facing the active matrix substrate and liquid crystal
intervening between the two substrates, wherein:
the active matrix substrate comprises a transparent substrate, on which a
plurality of scan lines, a plurality of signal lines crossing the scan
lines, switching elements provided at the intersections of the scan lines
and signal lines, pixel electrodes connected to the switching elements,
opposite electrodes and connecting electrodes provided on leading end
portions of the scan lines and signal lines are formed;
at least a connecting part of the connecting electrodes is formed by using
aluminum or alloy mainly composed thereof; and
in an active matrix substrate area with the intervening liquid crystal
present therein, an insulating film covers the surfaces of uppermost layer
scan lines, signal lines, electrodes of the switching elements and opposed
electrodes.
According to a sixth aspect of the present invention, there is provided a
liquid crystal display panel including an active matrix substrate, another
substrate facing the active matrix substrate and liquid crystal
intervening between the two substrates, wherein:
the active matrix substrate comprises a transparent substrate, on which a
plurality of signal lines, a plurality of switching elements provided at
the plurarity of signal lines, pixel electrodes connected to the switching
elements and connecting electrodes provided on leading end portions of the
signal lines are formed;
at least a connecting part of the connecting electrodes is formed by using
aluminum or alloy mainly composed thereof; and
portions of the signal lines in an area with the intervening liquid crystal
therein are covered by an insulating film.
According to the present invention, there is provided a method of
manufacturing a liquid crystal panel including an active matrix substrate,
another substrate facing the active matrix substrate and liquid crystal
intervening between the two substrates, comprising:
an active matrix substrate preparation step of forming a protective
insulating film on connecting electrodes of aluminum or an alloy mainly
composed thereof, forming the protecting insulating film with terminal
contact holes reaching the connecting electrodes, and forming, in a hot
water process, an insulating film consisting of a laminate film of
aluminum oxide and aluminum hydroxide on connecting portions of the
connecting electrodes;
the insulating film formed on the connecting portions of the connecting
electrodes being selectively removed in a step subsequent to the final
step in a subsequent liquid crystal display panel manufacturing process.
According to another aspect of the present invention, there is provided a
method of manufacturing a liquid crystal panel including an active matrix
substrate, another substrate facing the active matrix substrate and liquid
crystal intervening between the two substrates, comprising:
an active matrix substrate preparation step of forming connecting
electrodes of aluminum or an alloy mainly composed thereof, forming, in an
anodic oxidization or hot water process, an insulating film of aluminum
oxide or consisting of a laminate film of aluminum oxide and aluminum
hydroxide, forming a protective insulating film on the connecting
electrodes, and forming the protective insulating film with terminal
contact holes reaching the insulating film formed on the connecting
electrodes;
the insulating film formed on the connecting portions of the connecting
electrodes being selectively removed in a step subsequent to the final
step in a subsequent liquid crystal display panel manufacturing process.
According to other aspect of the present invention, there is provided a
method of manufacturing a liquid crystal panel including an active matrix
substrate, another substrate facing the active matrix substrate and liquid
crystal intervening between the two substrates, comprising:
an active matrix substrate preparation step of forming connecting
electrodes of aluminum of an alloy mainly composed thereof, and forming,
by an anodic oxidization or hot water process, an insulating film of
aluminum oxide or an insulating film consisting of a laminate film of
aluminum oxide and aluminum hydroxide on the connecting electrodes;
the insulating film formed on the connecting portions of the connecting
electrodes being selectively removed in a step subsequent to the final
step in a subsequent liquid crystal panel manufacturing step.
According to further aspect of the present invention, there is provided a
method of liquid crystal display comprising:
forming a terminal electrode part on an active matrix substrate of the
liquid crystal display connected to an external drive circuit by using
aluminum or an aluminum alloy, at least their surfaces connected to TCP
are covered with an insulating film of aluminum oxide or consisting of a
laminate film of aluminum oxide aluminum hydroxide; and
selectively removing the insulating film in a step subsequent to the final
step in a subsequent liquid crystal panel manufacturing step.
According to still further aspect of the present invention, there is
provided a method of manufacturing of a liquid crystal display panel
comprising steps of:
forming terminal electrodes by selectively forming a first metal film on a
transparent substrate;
forming an inter-layer insulating film with a terminal contact hole
reaching the first metal film;
selectively forming a second metal film, which is a single-layer film of
aluminum or an alloy thereof or a laminate film including an uppermost
layer of aluminum or an alloy thereof, in the terminal contact hole; and
forming a protective insulating film with a terminal contact hole.
According to other aspect of the present invention, there is provided a
method of manufacturing of a liquid crystal display panel comprising steps
of:
forming terminal electrode by selectively forming a first metal film on a
transparent substrate;
forming an inter-layer insulating film with a terminal contact hole
reaching the first metal film;
selectively forming a second metal film which is a single-layer film of
aluminum or an alloy thereof or a laminate film including an uppermost
layer of aluminum or an alloy thereof and an insulating film which is an
aluminum oxide film or a laminate film of aluminum oxide and aluminum
hydroxide thereon in the terminal contact hole, and
forming a protective insulating film and an insulating film with a terminal
contact hole reaching the second metal film.
According to still other aspect of the present invention, there is provided
a method of manufacturing of a liquid crystal display panel comprising
steps of:
forming terminal electrodes by selectively forming a first metal film on a
transparent substrate;
forming an inter-layer insulating film with a terminal contact hole
reaching the first metal film; and
selectively forming a second metal film, which is a single-layer film of
aluminum or an alloy thereof or a laminate film including an uppermost
layer of aluminum or an alloy thereof, in the terminal contact hole,
forming an insulating film, which is an aluminum oxide film or a laminate
film of aluminum oxide and aluminum hydroxide, to cover the surfaces of
uppermost layer lead lines and electrodes.
In the liquid crystal display panel according to the present invention, the
surfaces of connection terminals of aluminum or an alloy thereof, which
are to be connected to the TCP, are once covered with an insulating film
of aluminum oxide or forming by laminating aluminum oxide and aluminum
hydroxide, and this insulating film is selectively etched off in the final
step of the cell formation process, thus dispensing with any additional
photo-lithographic process, ensuring reliable electric connection of the
terminal electrode part to the TCP and improving the reliability of the
electric connection.
Other objects and features will be clarified from the following description
with reference to attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1(a) and 1(b) are a sectional view in a short side direction and a
plan view showing the terminal electrode of active matrix substrate of
liquid crystal display panel according to a first embodiment;
FIGS. 2(a) and 2(b) are a sectional view in a short side direction and a
plan view showing the terminal electrode of active matrix substrate of
liquid crystal display panel according to a second embodiment;
FIGS. 3(a) and 3(b) are a sectional view in short side direction and a plan
view showing the terminal electrode of active matrix substrate of liquid
crystal display panel according to the second embodiment;
FIGS. 4(a) and 4(b) are a sectional view in a short side direction and a
plan view showing the terminal electrode of active matrix substrate of
liquid crystal display panel according to a third embodiment;
FIGS. 5(a) and 5(b) are a sectional and a plan view showing a switching
element (TFT) in one-pixel part of the liquid crystal display panel
according the third embodiment;
FIGS. 6(a) and 6(b) are a sectional in short side direction and a plan view
showing the active matrix substrate of liquid crystal display panel
according to the third embodiment;
FIGS. 7(a) and 7(b) are a sectional view and a plan view showing a
switching element (TFT) part in a one-pixel part of the active matrix
substrate of the liquid crystal display panel;
FIGS. 8(a) and 8(b) are a sectional view in short side direction and a plan
view showing a further modification of the terminal electrode part of the
liquid crystal display panel according to the third embodiment;
FIGS. 9(a) and 9(b) are a sectional view and a pan view showing a still
further modification of the switching element (MIM) part of a one-pixel
part of the active matrix substrate according to the third embodiment;
FIGS. 10(a), 10(b) and 10(c) are sectional views and a plan view showing
the switching element (MIM) of an active matrix substrate, which is formed
in the application of Embodiments 1 and 2 to a liquid crystal display
panel of longitudinal electric field type;
FIGS. 11(a), 11(b) and 11(c) are sectional views and a plan view showing
the switching element (MIM) of an active matrix substrate, which is formed
in the application of Embodiments 1 and 2 to a liquid crystal display
panel of transversal electric field type;
FIGS. 12(a) and 12(b) are sectional views and a plan view showing other
modification of the switching element (MIM) of an active matrix substrate
according to the second embodiment;
FIGS. 13(a), 13(b) and 13(c) are drawings showing a method of manufacturing
of the third embodiment shown in FIGS. 4 and 5;
FIG. 14 is a sectional view showing the liquid crystal display panel;
FIG. 15 is a view showing the electric configuration of an active matrix
liquid crystal display panel using TFTS;
FIGS. 16(a) and 16(b) show the initial forced contact resistance and the
forced contact resistance after a high temperature, high relative humidity
preservation test conducted under conditions of 60 degrees C and 90%;
FIG. 17 is a sectional view of the substrate of thermal write type of
liquid crystal display disclosed in Japanese Patent Laid-Open No.
60-260920;
FIG. 18 is a sectional view of the active matrix substrate of
electro-optical apparatus of active matrix type disclosed in Japanese
Patent Laid-Open No. 3-280021; and
FIG. 19 is a sectional view of the thin film transistor array substrate
disclosed in Japanese Patent Laid-Open No. 8-122822.
PREFERRED EMBODIMENTS OF THE INVENTION
Preferred embodiments of the present invention will now be described with
reference to the drawings.
(Mode 1)
FIG. 1(a) is a sectional view taken along line I-I' in FIG. 1(b), i.e., in
a short side direction, showing a terminal electrode part of a liquid
crystal display panel concerning Mode 1 of the present invention. FIG.
1(b) is a plan view showing the same liquid crystal display panel.
Referring to these Figures, in the liquid crystal display panel concerning
Mode 1 of the present invention, terminal electrodes are each formed by
selectively forming a metal film 21 on a transparent substrate 11, forming
an inter-layer insulating film 22 with a terminal contact hole 25 reaching
the metal film 21, selectively forming a metal film 23 in the terminal
contact hole 25, and forming a protective insulating film 24 with a
terminal contact hole 26. The metal film 23 is a single-layer film of
aluminum or an alloy thereof or a laminate film including an uppermost
layer of aluminum or an alloy thereof.
With the liquid crystal display panel concerning Mode 1 of the present
invention as shown in FIGS. 1(a) and 1(b), the insulating film of aluminum
oxide or aluminum hydroxide may be formed on and removed from the terminal
electrode part without need of any photo-mask, and it is thus possible to
reduce the number of steps.
(Mode 2)
FIG. 2(a) is a sectional view taken along line I-I' in FIG. 2(b), i.e., in
a short side direction, showing a terminal electrode part of a liquid
crystal display panel in Mode 2 of the present invention. FIG. 2(b) is a
plan view showing the same liquid crystal display panel.
Referring to these Figures, in the liquid crystal display panel concerning
Mode 1 of the present invention, terminal electrode are each formed by
selectively forming a metal film 21 on a transparent substrate 11, forming
an inter-layer insulating film 22 with a terminal contact hole 25 reaching
the metal film 21, selectively forming a metal film 23 and an insulating
film 31 thereon in the terminal contact hole 25, and forming a protective
insulating film 24 and an insulating film 32 with a terminal contact hole
26 reaching the metal film 23. The metal film 23 is a single-layer film of
aluminum or an alloy thereof or a laminate film including an uppermost
layer of aluminum or an alloy thereof. The insulating film 31 is an
aluminum oxide film or a laminate film of aluminum oxide and aluminum
hydroxide.
In the above Modes 1 and 2 the metal film 21 is provided, but it is
possible to dispense with the metal film 21 and form the terminal
electrodes with the sole metal film 23.
(Mode 3)
15 FIGS. 4(a), 4(b), 5(a) and 5(b) show a liquid crystal display panel
concerning Mode 3 of the present invention. FIG. 4(a) is a sectional view
taken along line I-I' in FIG. 4(b), i.e., in a short side direction,
showing a terminal electrode part of the liquid crystal display panel
concerning Mode 3 of the present invention. FIG. 4(b) is a plan view
showing the same liquid crystal display panel. FIG. 5(a) is a sectional
view taken along line I-I' in FIG. 5(b) showing a switching element (TFT)
in one-pixel part of the liquid crystal display panel concerning Mode 3 of
the present invention. FIG. 5(b) is a plan view showing the same liquid
crystal display panel.
Referring to these Figures, in the liquid crystal display panel concerning
Mode 3 of the present invention, terminal electrodes are each formed by
selectively forming a metal film 21 on a transparent substrate 11, forming
an inter-layer insulating film 22 with a terminal contact hole 25 reaching
the metal film 21, and selectively forming metal film 23 in the terminal
contact hole 25.
The metal film 23 is a single-layer film of aluminum or an alloy thereof or
a laminate film including an uppermost layer of aluminum or an alloy
thereof. In an active matrix substrate area in which the intervening
liquid crystal is present, an insulating film 31 is formed to cover the
surfaces of uppermost layer lead lines and electrodes. The insulating film
31 is an aluminum oxide film or a laminate film of aluminum oxide and
aluminum hydroxide.
(Embodiment 1)
A specific example of the liquid crystal display panel concerning Mode 1 of
the present invention will now be described as Embodiment 1.
FIGS. 1(a) and 1(b) show Embodiment 1 Of the liquid crystal display panel
according to the present invention. The display panel comprises an active
matrix substrate 1, another substrate 2 facing the substrate 1, and liquid
crystal 4 intervening between the substrates 1 and 2. The active matrix
substrate 1 has TFTs as switching elements. This structure is the same as
the structure of the liquid crystal display panel shown in FIG. 14.
Referring to FIGS. 1(a) and 1(b), in Embodiment 1 the liquid crystal
display panel according to the present invention, terminal electrodes are
each formed by selectively forming a metal film 21 of an
aluminum/neodymium alloy about 200 nm thick on a transparent substrate 11
about 0.7 mm thick of glass, forming an inter-layer insulating film (i.e.,
gate insulating film) 22, which consists of a laminate layer a
low-temperature silicon oxide layer about 150 nm thick formed by
sputtering and a low-temperature silicon nitride about 350 nm thick formed
by plasma chemical gas phase growth, with a terminal contact hole 25
reaching the metal film 21, selectively forming a metal film 23, which
consists of a laminate layer of a molybdenum layer about 50 nm thick and
an aluminum/niodium alloy layer about 200 nm thick, in the terminal
contact hole 25, and forming a protective insulating film 24 of
low-temperature silicon nitride about 200 nm thick, for instance formed by
plasma chemical gas phase growth, with terminal contact hole 26 reaching
the metal film 23.
(Embodiment 2)
Referring to FIGS. 2(a) and 2(b), in Embodiment 2 the liquid crystal
display panel according to the present invention, terminal electrodes are
each formed by selectively forming a metal film 21 of an
aluminum/neodymium alloy about 200 nm thick on a transparent substrate 11
about 0.7 mm thick of glass, forming an inter-layer insulating film (i.e.,
gate insulating film) 22, which consists of a laminate layer a
low-temperature silicon oxide layer about 150 nm thick formed by
sputtering and a low-temperature silicon nitride about 350 nm thick formed
by plasma chemical gas phase growth, with a terminal contact hole 25
reaching the metal film 21, selectively forming a metal film 23, which
consists of a laminate layer of a molybdenum layer about 50 nm thick and
an aluminum/niodium alloy layer about 200 nm thick, and an insulating film
31 about 200 nm thick of tantalum oxide and aluminum oxide in the terminal
contact hole 25, and forming the insulating film 31 on the metal film 23
and a protective insulating film 24 about 200 nm thick of low-temperature
silicon nitride, for instance formed by plasma chemical gas phase growth,
with a terminal contact hole 26 reaching the metal film 23.
Embodiments 1 and 2 shown in FIGS. 1(a) and 1(b) and 2(a) and 2(b), are
examples of terminal electrode on an active matrix substrate, which uses
TFTs of an inverse stagger structure as switching elements. In these
examples, the scan line terminals 16 connect the scan lines 12 on the
transparent substrate 11 directly to the metal film 21, and the signal
line terminals 17 connect the signal lines 3 on the inter-layer insulating
film (i.e., gate insulating film) 22 to the metal film 21 via separate
contact holes (not shown).
FIGS. 10(a) to 10(c) show a one-pixel part of an active matrix substrate,
which is formed in the application of Embodiments 1 and 2 shown in FIGS.
1(a), 1(b), and 2(a), 2(b) according to the present invention to a liquid
crystal display panel of longitudinal electric field type. FIG. 10(a) is a
sectional view taken along line I-I' in FIG. 10(c), showing the one-pixel
part of the active matrix substrate in the application of Embodiment 1
shown in FIGS. 1(a) and 1(b). FIG. 10(b) is a sectional view taken along
line I-I' in FIG. 10(c), showing the one-pixel part of the active matrix
substrate in the application of Embodiment 2 shown in FIGS. 2(a) and 2(B).
FIGS. 10(a) to 10(c) show an example of channel etch type TFT.
Referring to FIGS. 10(a) and 10(b), a TFT 14 of bottom gate type is shown,
which is formed on a transparent substrate 11 having 0.7 nm thick of glass
and comprises, from the lower layer side, a gate electrode 56 about 200 nm
thick from aluminum/niodium alloy, an inter-layer insulating film (gate
insulating film) 22 formed as a lamination of a first gate insulating film
101 having 159 nm thick of low-temperature silicon oxide formed by
sputtering and a second gate insulating film 102 about 350 nm thick of
low-temperature silicon nitride formed by plasma chemical gas phase grow,
an island semiconductor layer 54 having 350 nm thick of amorphous silicon
facing the gate electrode 56 via the inter-layer insulating film 22, a
source and a drain electrode 52 and 53 formed in opposite side
spaced-apart portions of the island semiconductor layer 54 as a laminate
film consisting of a molybdenum film (Embodiment 1) or a tantalum nitride
film (Embodiment 2) about 50 nm and an aluminum/neodymium alloy film about
20 nm thick.
The gate electrode 56 is connected to a scan line 12 also about 200 nm
thick of aluminum/neodymium alloy. The source electrode 52 is connected to
a signal line 13 also formed as a laminate film consisting of a molybdenum
film (Embodiment 1) or a tantalum nitride film (Embodiment 2) about 50 nm
thick and an aluminum/neodymium alloy film about 200 nm thick. The drain
electrode 53 is connected to a pixel electrode 15 about 100 nm of ITO.
In Embodiment 2 shown in FIG. 10(b), an insulating film 31 about 200 nm
thick of tantalum oxide and aluminum oxide, covers the source and drain
electrodes 52 and 53 and the signal line 13. A semiconductor layer 54 is
formed as a laminate film consisting of a first semiconductor thin film
103 about 300 nm thick of amorphous silicon not doped with any impurity
and an n-type second semiconductor thin film 104 about 50 nm thick of
amorphous silicon not doped with phosphorus. The second semiconductor thin
film 104 is formed as separate portions on on the source and drain
electrodes 52 and 53.
FIGS. 11(a) and 11(b) show a one-pixel part of an active matrix substrate,
which is formed in applications of Embodiments 1 and 2 shown in FIGS.
1(a), 1(b) and 2(a), 2(b) to a liquid crystal display panel of a
transversal electric field type. FIG. 11(a) is a sectional view taken
along line I-I' in FIG. 11(c), showing the one-pixel part of the active
matrix substrate in the application of Embodiment shown in FIGS. 1(a) and
1(b) to the liquid crystal display panel of transversal electric field
type. FIG. 11(b) is a sectional view taken along line I-I' shown in FIG.
11(c), showing the one-pixel part of the active matrix substrate in the
application of Embodiment 2 shown in FIGS. 2(a) and 2(b) to the liquid
crystal display panel of transversal electric field type.
In the liquid crystal display panels of longitudinal electric field type
shown in FIGS. 10(a) and 10(b) the opposed electrode is formed on the
other substrate side, while in the liquid crystal display panels of
transversal electric field type shown in FIGS. 11(a) and 11(b), the
opposed electrode is formed on the active matrix substrate type. The pixel
electrode and the opposed electrode have comb-like shapes. However, the
TFT has the same structure in both types.
Referring to FIGS. 11(a) and 11(b), a TFT 14 of bottom gate type is shown,
which is formed on a transparent substrate 11 having 0.7 nm thick of glass
and comprises, from the lower layer side, a gate electrode 56 about 200 nm
thick from aluminum/niodium alloy, an inter-layer insuating film (gate
insulating film) 22 formed as a lamination of a first gate insulating film
101 having 159 nm thick of low-temperature silicon oxide formed by
sputtering and a second gate insulating film 102 about 350 nm thick of
low-temperature silicon nitride formed by plasma chemical gas phase grow,
an island semiconductor layer 54 having 350 nm thick of amorphous silicon
facing the gate electrode 56 via the inter-layer insulating film 22, a
source and a drain electrode 52 and 53 formed in opposite side
spaced-apart portions of the island semiconductor layer 54 as a laminate
film consisting of a molybdenum film (Embodiment 1) or a tantalum nitride
film (Embodiment 2) about 50 nm and an aluminum/neodymium alloy film about
20 nm thick.
A gate electrode 56 is connected to a scan line 12 also about 200 nm thick
of aluminum/neodymium alloy. A source and a drain electrode 52 and 53 are
connected to a signal line 13, which is also formed as a laminate film of
a molybdenum film (Embodiment 1) or a tantalum nitride film (Embodiment 2)
about 50 nm thick and an aluminum/neodymium alloy film about 200 nm thick,
and to a pixel electrode 15, respectively. The opposed electrode 19 is
formed from the same layer as the gate electrode 56, i.e., layer about 200
nm thick of aluminum/neodymium alloy, such that it faces the pixel
electrode 15.
In Embodiment 2 shown in FIG. 11(b), the source and drain electrodes 52,
53, the signal line 13 and the pixel electrode 15 are covered by the
insulating film 31 having the tantalum oxide of about 200 nm and the
aluminum oxide. The structure of semiconductor layer 54 is the same as
that of Embodiment 1 shown in FIG. 10.
A method of manufacturing the embodiments of the liquid crystal display
panels of longitudinal electric field type as shown in FIGS. 10(a) to
10(c), will now be described.
The gate electrode 56, the scan line 12 and the metal film 21 of the
terminal part are first formed by forming an aluminum/neodymium alloy film
about 200 nm thick by sputtering on the transparent substrate 11 having
0.7 mm thick of glass and photolithographically patterning the film. Then,
the gate insulating film 101 is formed by high frequency sputtering
low-temperature silicon oxide to a thickness of, for instance, about 150
nm.
Then, the island semiconductor layer 54 as the laminate consisting of the
intrinsic first semiconductor thin film 103 and the n-type second
semiconductor thin film 104, is formed by successively forming, by plasma
chemical gas phase growth, a low-temperature silicon nitride film about
350 nm thick, an amorphous silicon film about 300 nm thick free from doped
impurity and an amorphous silicon film 50 nm thick doped with phosphorus
and photolithographically patterning the films.
Then, the pixel electrode 15 is formed by sputtering ITO to a thickness of
about 100 nm lithographically patterning the film thus formed.
Then, the contact hole 25 is lithographically formed over the metal film 21
of the terminal electrode part.
Then, the source and drain electrodes 52 and 53, the signal line 13 and the
metal film 23 of the terminal electrode part, are formed by successively
sputtering forming, in Embodiment 2 a molybdenum film about 50 nm thick
and an aluminum/neodymium alloy film about 200 nm thick, and in Embodiment
2 a tantalum nitride film about 50 nm thick and an aluminum/neodymium
alloy about 300 nm thick, and hotographically patterning these films.
In Embodiment 2, the source and drain electrodes 52 and 53, the signal line
13 and the metal film 23 of the terminal electrode part are covered by the
insulating film 31 about 200 nm thick of tantalum and aluminum by
anodically oxidizing them in, for instance, a blend solution containing
1:9 of a solution obtained by neutralizing 3% tartaric acid with ammonia
water and ethylene glycol. The anodic oxidization is carried out by
applying gradually increasing DC voltage to an anodic oxidization terminal
such as to finally obtain a constant current of about 2 mA/cm.sup.2 and
finally holding a constant voltage of about 120 V for about 15 minutes.
Subsequently, the n-type second semiconductor thin film 104 is etchedly
patterned for channel formation by using the source and drain electrodes
52 and 53 as a mask.
Then, the protective insulating film 24, for instance about 200 nm thick,
of low-temperature silicon nitride is formed by plasma chemical gas phase
growth, and is then photolithographically formed with the hole 59 over the
pixel electrode 15 and the terminal contact hole 26 over the metal film 23
of the terminal electrode part.
In Embodiment 1, the insulating film 31 as the laminate film consisting of
an aluminum hydroxide film (upper layer) about 100 nm thick and an
aluminum oxide film (lower layer) about 50 nm thick, is formed on the
alumium/neodymium alloy connecting part surface of the metal film 23 by
carrying out, for instance, a hot water treatment at 70 degrees C for
about 10 minutes. Finally, an annealing process is carried out to complete
the substrate with the TFTs.
Afterwards, the substrate with the TFTs and the other substrate are
subjected to orientation film printing and sintering, and then to rubbing.
Then, the two substrates are held to define a space between them, and the
space is filled with liquid crystal. Then in the final step of the cell
formation process, the insulating film 31 of the connecting parts of the
terminal electrodes are selectively etched off, thus completing the liquid
crystal display panel.
Now, a method of manufacturing the embodiments of the liquid crystal
display panels of transversal electric field type as shown in FIGS. 11(a)
and 11(b) will be described.
The gate electrode 56, the scan line 12, the opposed electrode 19 and the
metal film 21 of the terminal part are first formed by forming an
aluminum/neodymium alloy film about 200 nm thick by sputtering on the
transparent substrate 11 having 0.7 mm thick of glass and
photolithographically patterning the film. Then, a first gate insulating
film 101 is formed by high frequency sputtering low-temperature silicon
oxide to a thickness of, for instance, about 150 nm.
Then, the island semiconductor layer 54 as the laminate consisting of the
intrinsic first semiconductor thin film 103 and the n-type second
semiconductor thin film 104, is formed by successively forming, by plasma
chemical gas phase growth, a low-temperature silicon nitride film about
350 nm thick, an amorphous silicon film about 300 nm thick free from doped
impurity and an amorphous silicon film 50 nm thick doped with phosphorus
and photolithographically patterning the films.
Then, the contact hole 25 is lithographically formed over the metal film 21
of the terminal electrode part.
Then, the source and drain electrodes 52 and 53, the signal line 13, the
pixel electrode 15 and the metal film 23 of the terminal electrode part,
are formed by successively sputtering forming in Embodiment 1 a molybdenum
film about 50 nm thick and an aluminum/neodymium alloy film about 200 nm
thick, and in Embodiment 2 a tantalum nitride film about 50 nm thick and
an aluminum/neodymium alloy about 300 nm thick, and photographically
patterning these films.
In Embodiment 2, the source and drain electrodes 52 and 53, the signal line
13, the pixel electrode 15 and the metal film 23 of the terminal electrode
part are covered by the insulating film 31 about 200 nm thick of tantalum
and aluminum by the anodically oxidizing as described above.
Subsequently, the n-type second semiconductor thin film 104 is etchedly
patterned for channel formation by using the source and drain electrodes
52 and 53 as a mask.
Then, the protective insulating film 24, for instance about 200 nm thick,
of low-temperature silicon nitride is formed by plasma chemical gas phase
growth, and the terminal contact hole 26 over the metal film 23 of the
terminal electrode part is then photolithographically formed.
In Embodiment 1, the insulating film 31 as the laminate film consisting of
an aluminum hydroxide film (upper layer) about 100 nm thick and an
aluminum oxide film (lower layer) about 50 nm thick, is formed on the
aluminum/neodymium alloy connecting part surface of the metal film 23 by
carrying out the foregoing hot water treatment. Finally, an annealing
process is carried out to complete the substrate with the TFTs.
Afterwards, like the above case the liquid crystal cells are formed, and in
the final step of the cell formation process, the insulating film 31 of
the connecting parts of the terminal electrodes are selectively etched
off, thus completing the liquid crystal display panel.
(Embodiment 3)
FIG. 3(a) is a sectional view taken along line I-I' in FIG. 3(a), i.e., in
short side direction, a terminal electrode part of a modification (i.e.,
Embodiment 3) of Embodiment 2 of the liquid crystal display panel
according to the present invention. FIG. 3(b) is a plan view showing the
same display panel.
Embodiment 3 of the liquid crystal display panel shown in FIGS. 3(a) and
3(b) according to the present invention, as shown in FIG. 14, comprises an
active matrix substrate 1, another substrate 2 and liquid crystal 4
intervening between the two substrates 1 and 2. The active matrix
substrate 1 uses MIMs as switching elements.
In Embodiment 3 of the liquid crystal display panel according to the
present invention, terminal electrodes are each formed by selectively
forming, on a transparent substrate 11 having 0.7 mm thick of glass, an
aluminum oxide film 23 about 200 nm thick of aluminum/tantalum alloy and
an insulating film 31 about 200 nm thick of aluminum oxide covering the
metal film 23, and forming the insulating film 31 on the metal film 23 and
an insulating film 24 about 200 nm thick of low-temperature silicon
nitride, formed by plasma chemical gas phase growth, with a terminal
contact hole 2 reaching the metal film 23. In this embodiment, a signal
line terminal 17 is such that the signal line 13 is directly connected to
the metal film 23.
FIG. 12(b) is a sectional view taken along line I-I', showing a switching
element (MIM) part in a one-pixel part of an active matrix substrate of
Embodiment 3 of the liquid crystal display panel. FIG. 12(b) is a plan
view showing the same one-pixel part.
An MIM 91 is shown, which is formed on the transparent substrate 11 having
0.7 mm thick of glass, which comprises a lower electrode 92 about 20 nm
thick of aluminum/tantalum alloy, an insulating film 31 about 200 nm thick
of aluminum oxide covering the lower electrode 92 and an upper electrode
13 about 150 nm thick of chromium. A protective insulating film 24 about
200 nm thick of low-temperature silicon nitride formed by plasma chemical
gas phase growth, covers the MIM 91.
The lower electrode 92 is connected to a signal line 13 also about 200 nm
thick of aluminum/tantalum alloy, and an upper electrode 93 is connected
to a pixel electrode 15 about 50 nm thick of ITO. The protective
insulating film 24 has an opening over the pixel electrode 15. The scan
line (i.e., scan electrode) is formed on the other side.
A method of manufacturing Embodiment 3 will now be described. First, an
aluminum/tantalum alloy is sputtering formed to a thickness of about 300
nm on the transparent substrate 11 0.7 nm thick of glass and
lithographically patterned to form the lower electrode 92 and the signal
line 13.
Then, as in the above case, the insulating film 31 about 200 nm thick of
aluminum oxide is formed anodically oxidizing the surfaces of the lower
electrode 92 and the signal line 13 in an oxidizing solution mainly
composed of tartaric acid, and then the upper electrode 13 is formed by
sputtering forming a chromium film about 150 nm thick and lithographically
patterning the film.
Then, the pixel electrode 15 is formed by sputtering forming ITO about 50
nm thick and lithogrphically forming the film thus formed.
Then, the protective insulating film 24 about 200 nm thick of
low-temperature silicon nitride is formed by plasma chemical gas phase
growth, and is then photo-lithographically formed with a hole 59 over the
pixel electrode 15 and a terminal contact hole 26 over the metal film 23
of the terminal electrode part.
Finally, annealing is executed to complete the substrate with the MIMs.
Afterwards, the substrate with the MIMs and the other substrate are
subjected to orientation film printing and sintering, and then to rubbing.
Then, the two substrates are held to define a space between them, and the
space is filled with liquid crystal. In the final step of the cell
formation process, the insulating film 31 on the connecting parts of the
terminal electrodes are selectively etched off, thus completing the liquid
crystal display panel.
As shown above, in Embodiment 3 the insulating film of aluminum oxide or as
the laminate film consisting of aluminum oxide and aluminum hydroxide is
formed on at least the connecting surface of the connecting terminal part
and, in the final step of the cell formation process, is selectively
removed. It is thus possible to eliminate adverse effects of aluminum
oxidization on the connecting terminal surface in the thermal processes
(such as annealing in the array formation process and orientation film
sintering in the cell formation process) and in the washing process, and
thus obtain a low and stable initial forced contact resistance of the
thermal electrode part.
FIG. 4(a) is a sectional view taken along line I-I', i.e., in short side
direction, showing a terminal electrode part of Embodiment of the liquid
crystal display panel according to the present invention. FIG. 4(b) is a
plan view showing the terminal electrode part. FIG. 5(a) is a sectional
view taken along line I-I', a switching element (TFT) part of a one-pixel
part of the active matrix substrate of the same panel. FIG. 5(b) is a plan
view showing the same one-pixel part.
Embodiment 3 of the liquid crystal display panel, as shown in FIG. 14,
comprises an active matrix substrate 1, another substrate 2 and liquid
crystal intervening between the substrates 1 and 2.
This embodiment is an example of the liquid crystal display panel of
longitudinal electric field type with the opposed electrodes formed on the
other substrate side. Referring to FIGS. 4(a) and 4(b), terminal
electrodes are each formed by selectively forming, on a laminate
inter-layer insulating film 41 about 300 nm thick of low-temperature
silicon oxide, formed by normal pressure chemical gas phase growth on the
transparent substrate 11 0.7 mm thick of glass, a metal film 21 as the
laminate film of an ITO film about 50 nm in thickness and a molybdenum
film about 150 nm thick, forming a second gate insulating film 42, for
instance about 300 nm thick of low-temperature silicon nitride formed by
plasma chemical gas phase growth, with a terminal contact hole 25 reaching
the metal film 21, and selectively forming a metal film 23 of
aluminum/tantalum alloy about 200 nm thick in the terminal contact hole
25.
In the TFT part shown in FIG. 5(a), on the transparent substrate 11 0.7 mm
thick of glass, are succesively formed a light-blocking film 51 about 150
nm thick of molybdenum, and an inter-layer insulating film 41 about 300 nm
thick of low-temperature silicon oxide formed by normal pressure chemical
gas phase growth. A TFT 14 of top gate type is formed on the inter-layer
insulating film 41 such that it faces the light-blocking film 51.
The TFT 14 is formed by successively laminating a source and a drain
electrode 52 and 53 about 50 nm thick of ITO, a laminate film consisting
of an island semiconductor layer 54 50 nm thick of amorphous silicon,
formed on the source and drain electrodes 52 and 53, and a first gate
insulating film 55 about 50 nm thick of low-temperature silicon nitride,
formed by plasma chemical gas phase growth, a second gate insulating film
42 about 300 nm thick of low-temperature silicon nitride, formed by plasma
chemical gas phase growth, and a gate electrode 56 about 200 nm thick of
an aluminum/titanium/tantalum alloy, facing the island semiconductor layer
54 via the gate insulating films 55 and 42.
The gate electrode 56 is connected to a scan line 12 also of the
aluminum/titanium/tantalum alloy, the source electrode 52 is connected to
a signal line 13 as a laminate film consisting of an ITO film about 50 nm
thick and a molybdenum film about 150 nm thick, and the drain electrode 53
is connected to a pixel electrode 15 also of the ITO.
An insulating film 31, which is formed as an aluminum oxide film about 200
nm thick or a laminate film consisting of an aluminum hydroxide film about
150 nm thick and an aluminum oxide film about 100 nm thick, covers the
scan line 12 and the gate electrode 56.
The island semiconductor layer 54 is formed by laminating an n-type first
semiconductor thin film 57 about 5 nm of phosphorus-doped amorphous
silicon, which is formed as separate portions on the sides of the source
and drain electrodes 52 and 53, and a second semiconductor thin film 58
about 45 nm of non-impurity-containing amorphous silicon.
Embodiment 3 is an example of an active matrix substrate using TFTs having
a forward stagger structure as switching elements. In this structure, the
signal line terminal 17 is connected by the signal line 13 directed by the
signal line formed on the transparent substrate 11 to the metal film 21 of
the terminal electrode part, and the scan line terminal 16 is connected by
the scan line formed the second gate insulating film 42 to the metal film
21 in a separate contact hole (131 in FIG. 13(a)).
A method of manufacturing Embodiment 3 will now be described with reference
to FIGS. 13(a) to 13(b). The light-blocking film 51 is formed by
sputtering forming a molybdenum film about 150 nm thick and
photolithographically patterning the film. Then, the inter-layer
insulating film 41 about 300 nm thick of low-temperature silicon oxide is
formed by normal pressure chemical gas phase growth.
Then, lower layer films of the source and drain electrodes 52 and 53, the
pixel electrode 15 and the signal line 13 are sputtering formed by
sputtering an ITO film about 50 nm and photolithographically patterning
the film.
Then, their surface portions are doped with phosphorus by plasma treating
them with phosphine (PH.sub.3). Then, the laminate film of the island
semiconductor film 54 and the first gate insulating film 55, is formed by
successively forming a non-impurity-doped amorphous silicon layer about 50
nm thick and a low-temperature silicon nitride film of the same thickness
y plasma chemical gas phase growth and patterning these films.
The plasma chemical gas phase growth is carried out by holding the
substrate temperature at about 300 degrees C. In this process, phosphorus
in surface portions of the source and drain electrodes 52 and 53 are thus
diffused in the intrinsic amorphous silicon film, thus forming the n-type
semiconductor thin film 57 about 5 nm and effecting electric connection of
the source and drain electrodes to the semiconductor layer.
Then, the signal line 13 is formed by sputtering forming a molybdenum layer
about 150 nm thick and lithographically patterning the film.
Then, the second gate insulating film 42 about 300 nm thick of
low-temperature silicon nitride is formed by plasma chemical gas phase
growth, and is photoliothographically formed with a hole 59 over the pixel
electrode 15 and the terminal contact hole 25 over the metal film 21 of
the terminal electrode part.
Then, the gate electrode 56, the scan line 12 and the metal film 23 of the
terminal electrode part are formed by sputtering forming an
aluminum/titanium/tantalum film about 300 nm thick and
photolithographically patterning the film. Then, like Embodiment 2, their
surfaces are covered with the insulating film 31 as an aluminum oxide film
about 200 nm thick by anodically oxidizing their surfaces in an oxidizing
solution mainly composed of tartaric acid. Alternately, like Embodiment 1,
their surfaces are covered with the insulating film 31 as a laminate film
consisting of an aluminum hydroxide film (i.e., upper film) about 150 nm
thick and an aluminum oxide film (i.e., upper film) about 100 nm thick by
a hot water treatment carried out at 700 degrees C for about 20 minutes.
Finally, annealing is made to complete the substrate with the TFTs (FIG.
13(a)).
Afterwards, the substrate with the TFTs and the other substrate are
subjected to orientation film printing and sintering, and then to rubbing.
Then, the two substrates are held to define A space between them, and the
space is filled with liquid crystal (FIG. 13(b)).
Then in the final step of the cell formation process, the insulating film
31 of the connecting parts of the terminal electrodes are selectively
etched off, thus completing the liquid crystal display panel (FIG. 13(c)).
(Embodiment 4)
FIG. 6(a) is a sectional view taken along line I-I', in short side
direction, showing a different modification (Embodiment 4) Embodiment 3 of
the liquid crystal display panel according to the present invention. FIG.
6(b) is a plan view showing the same display panel. FIG. 7(a) is a
sectional view showing a switching element (TFT) part in a one-pixel part
of the active matrix substrate of the display panel. FIG. 7(b) is a plan
view showing the same one-pixel part.
Embodiment 4 of the liquid crystal display panel, as shown in FIG. 14,
comprises an active matrix substrate 1, another substrate 2 and liquid
crystal 4 intervening between the substrates 1 and 2. Embodiment 4 is an
example of the liquid crystal display panel of transversal electric field
type, with the opposed electrode formed on the active matrix side.
Referring to FIGS. 6(a) and 6(b), terminal electrodes are formed by
selectively forming a metal film 21 having 200 nm thick of
aluminum/neodymium alloy on the transparent substrate 11 having 0.7 mm
thick of glass, forming an inter-layer insulating film (gate insulating
film) 22 as the laminate, for instance, consisting of a low-temperature
silicon oxide film about 150 nm thick, formed by sputtering, and a
low-temperature silicon nitride film about 150 nm thick, formed by plasma
chemical gas phase growth.
Referring to FIGS. 7(a) and 7(b), the TET 14, of bottom type, is formed by
successively forming the transparent substrate 11 0.7 mm thick of glass,
comprises a gate electrode 56 about 200 nm of an aluminum/neodymium alloy,
an inter-layer insulating film (gate insulating film) 22 formed as a
laminate film consisting of a first gate insulating film 101 about 150 nm
thick of aluminum/neodymium alloy and a second gate insulating film 102
about 350 nm thick of low-temperature silicon nitride, formed by, plasma
chemical gas phase growth, an island semiconductor layer 54 about 350 nm
thick of amorphous silicon facing a gate electrode 56 via the inter-layer
insulating film 2, a source and a drain electrode 52 and 53 formed as
separate film portions about 300 nm thick of molybdenum on the island
semiconductor layer 54, and a protective insulating film 24, for instance
about 200 nm thick of low-temperature silicon nitride, formed by plasma
chemical gas phase growth.
A gate electrode 56 is connected to a scan line 12 also about 200 nm of an
aluminum/neodymium alloy, and the source and drain electrodes 52 and 53
are connected to a signal line 13 also about 300 nm thick of molybdenum
and a comb-like pixel electrode 15, respectively.
An opposed electrode is covered by an insulating film 3 formed as an
aluminum oxide film about 200 nm thick or a laminate film consisting of an
aluminum oxide film about 150 nm and aluminum oxide film about 100 nm. The
semiconductor layer 54 has the same structure as described before in
connection with Embodiment 1 (FIG. 10(a) and 10(b)).
Embodiment 4 is an example of an active matrix substrate using TFTs having
an inverse stagger structure as switching elements. In this case, a scan
line terminal 16 is connected directly by the scan line 12 on the
transparent substrate 11 to the metal film 21, and a signal line terminal
17 is connected by the signal line on the inter-layer insulating film
(gate insulating film) 2 to the metal film 23.
A method of manufacturing Embodiment 3 will now be described. First, the
gate electrode 56, the scan line 12 and the metal film 21 of the terminal
part are formed by sputtering forming an aluminum/neodymium alloy film
about 200 nm thick on the transparent substrate 11 having 0.7 nm thick of
glass and photolithographically sputtering these films. Then, a
low-temperature oxide silicon about 150 nm thick is high frequency
sputtering formed as a first gate insulating film 101.
Then, an island semiconductor layer 54 is formed by successively laminating
a low-temperature silicon nitride film about 350 nm thick, a
non-impurity-doped amorphous silicon film and a phosphorus-doped amorphous
film about 50 nm thick and photolithographically patterning the films.
Then, the terminal contact hole 25 is formed over the metal film 21 of the
terminal electrode part.
Then, the source and drain electrodes 52 and 53, the signal line 13, the
pixel electrodes 15 and the metal film 23 of the terminal part by
sputtering forming a molybdenum film about 300 nm thick and
photolithographically patterning the film.
Then, a channel is formed by etching the n-type second semiconductor thin
film 104 with the source and drain electrodes 52 and 53 as mask.
Then, a low-temperature silicon nitride film about 200 nm thick is formed
as the protective insulating film 24 by plasma chemical gas phase growth,
and is then photolithogaphically formed with the terminal contact hole 26
over the metal film 23 of the terminal part.
Then, the opposed electrode 19 and the metal film 64 of the terminal
electrode part are formed by sputtering forming an aluminum/neodymium
alloy film about 300 nm thick and photlithographically patterning the
film. Then, like Embodiment 2, the opposed electrode 19 and the metal film
64 is covered by the insulating film 31, formed as an aluminum oxide film
about 200 nm thick by anodically oxidizing them in an oxidizing solution
mainly composed of tartaric acid. Alternately, like Embodiment 3, the
opposed electrode 19 and the metal film 64 is covered by the insulating
film 31, formed as a laminate film consisting of an aluminum hydroxide
film (upper layer) about 150 nm thick and an aluminum oxide film (lower
layer) about 100 nm thick by carrying out a hot water treatment at 70
degrees C.
Finally, annealing is carried out to complete the substrate with the TFTs.
Afterwards, the substrate with the TFTs and the other substrate are
subjected to orientation film printing and sintering, and then to rubbing.
Then, the two substrates are held to define a space between then, and the
space is filled with liquid crystal. Then, as in Embodiments 1 and 2, in
the final step of the cell formation process, the insulating film 31 of
the connecting part of the terminal electrode are successively etched off,
thus completing the liquid crystal display panel.
(Embodiment 5) FIG. 8(a) is a sectional view taken along line I-I' in FIG.
8(a), i.e, in short side direction, showing a terminal electrode part of a
further modification (Embodiment 5) of Embodiment 3 of the liquid crystal
display panel according to the present invention. FIG. 8(b) is a plan view
showing the same terminal electrode part. FIG. 9(a) is sectional view
taken along line I-I' in FIG. 9(b), showing a switching element (MIM) part
of a one-pixel part of the active matrix substrate of the same display
panel. FIG. 9(b) is a pan view showing the same one-pixel part.
This liquid crystal display panel, as showing FIG. 14, comprises an active
matrix substrate 1, another substrate 2 and liquid crystal intervening
between the substrates 1 and 2.
As shown in FIGS. 8(c) and 8(b), terminal electrodes are formed by
selectively forming a metal film 23 about 200 nm thick of an
aluminum/titanium/tantalum alloy on an underlying insulating film 81 about
50 nm thick of tantalum oxide, which is formed on a transparent substrate
11 0.7 mm thick of glass.
Referring to FIGS. 9(a) and 9(b), on an underlying insulating film 81 about
50 nm thick of tantalum oxide, formed on a transparent substrate 11 0.7 nm
thick of glass, an MIM 91 is formed by successively laminating a lower
electrode 92 as an aluminum/titanium/tantalum alloy about 200 nm thick, an
insulating film 31 about 200 nm thick of aluminum oxide covering the lower
electrode 92, and an upper electrode 13 about 150 nm thick of chromium.
The lower electrode 92 is connected to a signal line 13 also about 200 nm
thick of an aluminum/titanium/tantalum alloy, and the upper electrode 93
is connected to a pixel electrode 15 about 50 nm of ITO. In Embodiment 5
the signal line is directly connected to the metal film 23. The scan line
(i.e., scan electrode) is formed on the other substrate side.
A method of manufacturing Embodiment 5 will now be described. First, the
lower electrode 92, the signal line 13 and a metal film 23 of the terminal
electrode part are formed by successively sputtering laminating a tantalum
oxide film about 50 nm and an aluminum/titanium/tantalum alloy about 30 nm
thick on a transparent substrate 11 0.7 nm thick of glass and
photolithographically patterning the aluminum/titanium/tantalum alloy.
Then, like Embodiment 2, the lower electrode 92, the signal line 13 and the
metal film 23 of the terminal electrode part, is covered with the
insulating film 31 about 200 nm thick of aluminum oxide, formed by
anodically oxidizing them in an oxidizing solution mainly composed of
tartaric acid. Then, the upper electrode 93 is formed by sputtering
forming a chromium film about 150 nm thick and photolithographically
patterning the film.
Then, the pixel electrode 15 is formed by sputtering forming an ITO film
about 50 nm thick and photolithographically patterning the film. Finally,
annealing is made to complete the substrate with the MIMs. Afterwards, the
substrate with the MIMs and the other substrate are subjected to
orientation film printing and sintering, and then to rubbing. Then, the
two substrates are held to define a space between them, and the space is
filled with liquid crystal.
Then in the final step of cell formation process, the insulating film 31 of
the connecting parts of terminal electrodes are successively etched off,
thus completing the liquid crystal display panel.
While the method of manufacturing Embodiment 3 has been described before as
a typical method according to the present invention in connection with
FIGS. 13(a) and 13(b), the same method is also applicable to the other
embodiments. In addition, while in the above embodiments the insulating
film 32 is selectively removed by wet etching in the final step of the
cell formation process, it is also possible to remove the film 3 by
mechanically polishing the connecting terminal surface. Furthermore, it is
possible to remove the film 31 prior to press bonding the TCP in a liquid
crystal module assembling process. Moreover, while the channel etch type
TFT has been described as an example of the inverse stagger type TFT in
the above embodiments, the present invention is also applicable to a TFT
of channel protection type.
The fact that a laminate film consisting of an aluminum hydroxide (i.e., an
upper layer) and an aluminum oxide (i.e., a lower layer) is formed in the
case of forming the insulating film 31 by a hot water treatment, is
experimentally confirmed by the inventor, and is different from the prior
art technique disclosed in the Japanese Patent Disclosure No. 60-260920.
This is so because according to the disclosure probably the analysis is
made only about the film surface.
As shown above, an insulating film of aluminum oxide or as a laminae film
consisting of an aluminum oxide film and an aluminum hydroxide film, is
preliminarily formed on the surface of the connecting terminal, and is
selectively removed before the cell formation process or press bonding the
TCP in the module formation process. It is thus possible to eliminate the
adverse effects of oxidizing aluminum on the connecting terminal surface
in the heat treatment processes (such as the annealing in the array
formation process or the orientation film sintering in the cell formation
process) and ensure that the initial forced contact resistance in the
terminal electrode part is low and stable.
In addition, by setting the thickness of the insulating film 3 to be 100 nm
or above, it is possible to use alkali or acid for the washing in the cell
formation process and eliminate the generation of hilloc on the aluminum
surface of the terminal electrode part, thus improving the yield and the
reliability.
Although a natural aluminum oxide film is formed on the surface of the
connecting terminal part, its thickness is no greater than 5 nm, and it
can be readily broken apart by ACF particles when press bonding the TCP
and ensure stable connection resistance and reliability.
FIGS. 16(a) and 16(b) show examples of the forced contact resistance in the
case of Embodiment 3 of the present invention and the prior art aluminum
terminal case. Specifically, FIG. 16(a) shows the initial forced contact
resistance, and FIG. 16(b) shows the forced contact resistance after a
high temperature, high relative humidity preservation test conducted under
conditions of 60 degrees C and 90%. The resistance shown is the resultant
resistance of 20 terminals connected in series. The ACF used was of a new
version of "CP7131" manufactured by Sony Chemical. The press bonding was
conducted under conditions of 180 degrees C and 30 Kg/cm.sup.2, the heat
treatment was conducted under conditions of 3,300 degrees C an 30 minutes,
and the hot water treatment in the washing was conducted under conditions
of 70 degrees C and 10 minutes.
As is obvious from FIGS. 16(a) and 16(b), in the prior art aluminum
terminal manufacture method an insulating film is formed on the aluminum
terminal surface, and it is thus impossible to obtain electric connection
at the terminal electrode part. In contrast, according to the present
invention it is possible to obtain a low and stable initial contact force
resistance and thus improve the connection reliability.
As has been described in the foregoing, according to the present invention
it is possible to dispense with the photolithography once in the array
formation process, thus improving the yield and the reliability. This is
so because it is possible to form and remove the insulating film of
aluminum oxide or aluminum hydroxide in the terminal electrode part
without any photo-mask, thus reducing the number of steps involved.
It is also possible to obtain a low and stable initial forced contact
resistance in the terminal electrode part and improve the connection
reliability as well. This is so because an insulating film of aluminum
oxide or aluminum hydroxide is preliminarily formed on at least the
surface of the connecting electrode of the terminal part, which is to be
in contact with the TPC, and selectively removed in the final step of the
cell formation process, so that it is possible to prevent oxidization or
hydroxidization of the connecting surface of aluminum in the subsequent
heat treatment processes (i.e., the annealing in the array formation
process and the orientation film sintering in the cell formation process),
the hot water treatment in the washing process and steam drying.
Furthermore, it is possible to reduce display irregularities and improve
the yield and there liability. This is so because an insulating film of
aluminum oxide or aluminum hydroxide is preliminarily formed to cover
exposed aluminum of the terminal electrode part, so that it is possible to
adopt washing with alkali or acid in the cell formation process and
sufficiently remove alkali ions and chlorine ions.
Still further, in Embodiments 2 and 3, it is possible to protect the
uppermost layer aluminum lead lines electrodes in the pixel part from
water intrusion from the orientation film or the like and thus prevent
corrosion of aluminum.
Moreover, it is possible to improve the yield and productivity in the cell
formation process. This is so because an insulating film of aluminum oxide
or aluminum hydroxide is preliminarily formed on the aluminum surface of
the terminal electrode part, so that it is possible to prevent hilloc
generation and also prevent damages to the orientation film in the
terminal electrode part and contamination of the rubbing roll in the
rubbing in the cell formation process.
Changes in construction will occur to those skilled in the art and various
apparently different modifications and embodiments may be made without
departing from the scope of the present invention. The matter set forth in
the foregoing description and accompanying drawings is offered by way of
illustration only. It is therefore intended that the foregoing description
be regarded as illustrative rather than limiting.
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